Segment V9.3: Laminar/Turbulent Transition

(Related to Textbook Section 9.2.1 - Boundary Layer Structure & Thickness on a Flat Plate)

Near the leading edge of a flat plate, the boundary layer flow is laminar. If the plate is long enough, the flow becomes turbulent, with random, irregular mixing. A similar phenomenon occurs at the interface of two fluids moving with different speeds.

As shown in a computational fluid dynamic simulation, the interface between two fluids moving horizontally with different speeds becomes unstable and waves develop on the surface. Similarly, the rising smoke plume from a cigarette is laminar near the source, becomes wavy at a certain location, and then breaks into turbulence. (CFD video courtesy of ITS Corp.)